EAR 105 1st Edition Lecture 10Outline of Last Lecture I. Mass WastingII. Running WaterOutline of Current Lecture III. RiversIV. Ground WaterV. GlaciersCurrent LectureIII. Rivers- A stream’s load (how much sediment it can carry) is related to its competence and capacityo Competence: maximum particle sizeo Capacity: maximum discharge- Based on nature of water flow, a stream will either be erode sediment, depositing it, or just continuing to transport it- Between uplands and lowlands, streams transport water; near the mouth, streams deposit it.o (Near the mouth, slope is much gentler, thus conducive to deposition)- Rivers change patterns according to the easiest path of movemento i.e. when certain areas flood, the flow of water will shift to a different channel- Rivers have deltas, natural levees, o Deltas have a bird’s foot like appearance; occur near the outlet of a given rivero Natural levees parallel the bank of the river— coarser particles accumulate first and are topped by progressively finer-grained materials Natural levees raise gradually over time. Humans build levees to keep a river bound to its channel- causing the displacement of water flow. This usually leads to disproportionately more water somewhere else, usually downstreamo Meandering streams: move in sweeping bendsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. When water flow undergoes a bend, the water on the outside is more fast flowing  erosive than that on the inside. Meandering streams are characterized by point bars and cut banks.- The more erosive water thus forms a cut bank—an area wherethe water cuts away at the floodplain Point bars: form along inside of curves of channel where sand is deposited and accumulated Meandering rivers form oxbow lakes when they develop cut-offs- Cut-offs occur when the stream decides to take short cuts in the meandering path in order to become more efficient- When the cut-offs fill in, the oxbow lake is formedo Braided streams: move in complex networks of channels Relatively slow-moving, filled with sand/ sediment- Base level refers to the lowest point a stream can erode to.o By definition, streams carry water from high to low—the lowest point is the base level If a dam is introduced in the stream flow, the resulting occurrence may be a localized flood,- Valley sides are shaped by weathering, overland flow, and mass wasting—all of which are catalyzed by water flowo Narrow V-shaped valleys widen via processes of mass wasting  meandering rivers - Floods are the most common and costly geologic hazardo Caused by weather events, by extension, human interference with stream system (as it relates to poorly constructed dams)o Regional floods vs. flash floods Regional floods occur gradually in lowlands. Takes a while for water toaccumulate and to deplete ex. Mississippi River basin Flash floods occur violently when water flows suddenly- Floods are the most deadly type of natural disaster in the USo Flood control efforts Engineering efforts—artificial levees, flood-control dams, channelization Nonstructural approach through sound floodplain managementIV. Ground Water- Ground Water: generally, water that exists below the Earth’s surfaceo Water percolates through the unsaturated zone through porous layers of the Eartho Eventually, the water reaches the zone of saturationo Overuse of ground water via mining depresses the groundwater level (centered on a cone of depression)  This results in the depletion of the groundwater level for up to 30 ft—taking a significant toll on the sustainability of land.o Ground water systems are slow moving and should be treated as nonrenewable resourceso They are also highly susceptible to contamination as a result of plant pesticides intermingling with runoff water. (Runoff water percolates into the groundwater reserve)V. Glaciers (from video accessible on Blackboard)- Moving glaciers disintegrates underlying ground—resulted historically in the formation of major geographical boundaries as in the US, China, and Russia- Glaciers result from accumulation of snow in areas of extreme cold and high altitude- Glaciers form when the accumulation of snow in the winter outweighs depletion in the summer. - The yearly accumulation of snow compacts, becoming air-tight, and form an intermediate material called firn—between ice and snow- Ice must accumulate to 20meters if thickness before it can start to